Structure and method for separation and transfer of semiconductor thin films onto dissimilar substrate materials

ABSTRACT

A method for placing nitride laser diode arrays on a thermally and electrically conducting substrate is described. The method uses an excimer laser to detach the nitride laser diode from the sapphire growth substrate after an intermediate substrate has been attached to the side opposite the sapphire substrate. A secondary layer is subsequently deposited to act as a transfer support structure and bonding interface. The membrane is released from the intermediate substrate and a thermally conducting substrate is subsequently bonded to the side where the sapphire substrate was removed. Similarly, the secondary layer may be used as the new host substrate given an appropriate thickness is deposited prior to removal of the intermediate substrate.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of laser diodes,and more particularly to transfer of short-wavelength nitride-basedlaser diodes from transparent substrate materials onto dissimilarsubstrates.

Short-wavelength nitride based laser diodes provide smaller spot sizeand a better depth of focus than red and infrared (IR) laser diodes forlaser printing operations and other applications. Single-spot nitridelaser diodes have applications in areas such as optical storage.

Laser diode arrays are desirable for application to high-speed laserprinting. Printing at high speeds and at high resolution requires laserarrays due to the fundamental limits of polygon rotation speed, laserturn-on times and laser power. Laser diode arrays have previously beenemployed using red and infrared laser diode structures. Dual-spot redlasers and quad-spot infrared lasers have been used for laser printers.

Laser diodes based on higher bandgap semiconductor alloys such asAlGalnN have been developed. Excellent semiconductor lasercharacteristics have been established in the near-UV to violet spectrum,principally by Nichia Chemical Company of Japan. See for example, S.Nakamura et al., “CW Operation of InGaN/GaN/AlGaN-based laser diodesgrown on GaN substrates”, Applied Physics Letters, Vol. 72(16), 2014(1998) and S. Nakamura and G. Fasol, “The Blue Laser Diode-GaN basedLight Emitters and Lasers”, (Springer-Verlag, 1997), A. Kuramata et al.,“Room-temperature CW operation of InGaN Laser Diodes with VerticalConducting Structure on SiC Substrate”, Japanese Journal of AppliedPhysics, Vol. 37, L1373 (1998) all of which are incorporated byreference in their entirety.

Extension of dual-spot lasers or quad-spot lasers to shorter wavelengthsenables printing at higher resolution. The architecture for shortwavelength laser diodes has needed to be different because of themisalignment of the crystallographic orientation between the sapphireand the GaN epitaxial layer. Therefore mirror facets formed by cleavingon laser diodes with sapphire substrates exhibit increased surfaceroughness and reduced reflectivity. The growth on sapphire substrateshas also required that the p-electrode and n-electrode have to be formedon the same surface, typically with a lateral n-contact in contrast tolaser diodes on conductive substrates which have a backside n-contact.

A group from the University of California has developed a technique forseparation of GaN films from sapphire substrates using an UV-excimerlaser. The University of California technique uses an ultravioletexcimer laser to decompose a thin portion of the GaN layer at theinterface with the sapphire substrate. By proper adjustment of theexcimer laser flux, the interfacial GaN is decomposed into Ga and N withminimal damage. Subsequently, the GaN film is removed by gentle heatingof the remaining Ga metal which has a melting point of 30° C. at thefilm-substrate interface. See W. S. Wong et al., “Damage-free separationof GaN thin films from sapphire substrates”, Applied Physics Letters,Vol. 72, 599 (1998) which is incorporated by reference in its entirety.

SUMMARY OF THE INVENTION

Architectures using insulating substrates allow the economicalconstruction of nitride based laser diodes and laser diode arrays.Currently, most advanced nitride based single laser structures are grownon insulating sapphire (Al₂O₃) substrates which are opticallytransparent. The use of optically transparent insulating substrates forlaser diode arrays presents a special problem in providing electricalcontacts for the laser diodes. In contrast to the situation whereconducting substrates are used, insulating substrates cannot provide acommon backside contact for all laser diodes in an array. Hence,providing electrical contacts to laser diode arrays on insulatingsubstrates has required the use of special architectures.

In an embodiment in accordance with the invention, removal of theoptically transparent insulating substrate after growth of the laserdiode or laser diode array structures simplifies providing electricalcontacts to the laser diode or laser diode arrays and avoids specialarchitectures while allowing a superior heat sink to be attached to thelaser diode or laser diode arrays. The laser diode or laser diode arraymay be attached to a thermally conductive wafer or directly mounted ontoa heatsink after substrate removal by soldering, thermo-compressionbonding or other means well known to those of ordinary skill in the art.Removal of the optically transparent insulating substrate requires theattachment of a support substrate as an intermediate step. Subsequenttransfer of the laser diode or laser diode array after removal of thesupport substrate requires a secondary support to provide mechanicalrigidity to the laser diode or laser diode array. Adding a thermallyconductive substrate to the laser diode or laser diode array beforeremoval of the insulating substrate allows positioning of the thermallyconductive substrate on the side of the laser diode or laser diode arraycloser to the laser active region for more effective heat sinking thanif the laser diode or laser diode array is attached to the thermallyconductive substrate after removal of the insulating substrate. This isparticularly important in the case of independently addressable laserdiode arrays used in high-resolution and high-speed printing. Anycross-talk between laser diodes in an array adversely effects theperformance of the printing system and is to be avoided. Thermalcross-talk is a major component in the case of nitride based lasersgrown on sapphire because of the comparatively poor thermal conductivityof the sapphire substrate. Removal of the sapphire substrate greatlyreduces the thermal impedance and consequently any thermal cross-talk isalso reduced.

The nitride laser membrane may be cleaved to create parallel mirrorfacets before attachment to the new host substrate. The nitride lasermembrane may also be aligned during the attachment and transfer processwith a new crystallographically oriented host substrate and cleaved toform mirror facets for the laser diode or laser diode array. Cleavedrather than etched mirror facets result in perfectly parallel, vertical,and smooth mirrors which are critical for properly optimized laseroperation. Also a free-standing nitride laser membrane may be cleaveddirectly without attachment to any substrate to form high-quality mirrorfacets.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained and understood by referringto the following detailed description and the accompanying drawings inwhich like reference numerals denote like elements as between thevarious drawings. The drawings, briefly described below, are not toscale.

FIGS. 1a-1 g show the steps for removing the sapphire growth substrateand adding a thermally and electrically conducting substrate to a laserstructure in an embodiment in accordance with the invention.

FIG. 1h shows a laser diode array structure in an embodiment inaccordance with the invention.

FIGS. 2a-2 b show the steps for removing the sapphire growth substrateand depositing a new thermally conductive host substrate onto a laserdiode structure in an embodiment in accordance with the invention.

FIGS. 3a-3 b show the steps for removing the sapphire growth substrateand depositing a new thermally and electrically conductive hostsubstrate onto a laser diode structure in an embodiment in accordancewith the invention.

FIG. 4 shows crystal planes of silicon and InGaAIN membrane.

FIG. 5 shows cleaved facets in InGaAIN membrane in an embodiment inaccordance with the invention.

FIG. 6 shows crystal planes of silicon and InGaAIN membrane.

FIG. 7 shows cleaved facets in InGaAIN membrane in an embodiment inaccordance with the invention.

DETAILED DESCRIPTION

In the following detailed description, numeric ranges are provided forvarious aspects of the embodiments described. These recited ranges areto be treated as examples only, and are not intended to limit the scopeof the claims hereof. In addition, a number of materials are identifiedas suitable for various facets of the-embodiments. These recitedmaterials are to be treated as exemplary, and are not intended to limitthe scope of the claims hereof.

With respect to FIG. 1a, removal of optically transparent substrate 215is useful for nitride laser diodes because removal of opticallytransparent substrate 215 allows advantages that include realization ofa vertical electrical contact structure, better heat sinking and mirrorfacets that are cleaved.

In an embodiment in accordance with the invention, FIGS. 1a-1 gschematically show the steps for removal of optically transparentsubstrate 215, typically sapphire, by laser liftoff and bonding ofsemiconductor membrane 1110 to thermally conductive final substrate 1138using supporting substrate 1105. Semiconductor membrane 1110 istypically an InGaAIN type film. Initially, backside 1115 of opticallytransparent substrate 215 is polished to a very smooth surface finish toreduce light scattering off backside 1115. Polishing is accomplishedmechanically using a succession of diamond pads. During the polishingprocedure, the diamond grit size is gradually reduced from 30 μm gritdown to 0.1 μm grit. An optimal grit size of 16 μm is sufficient toreduce the light scattering from backside 1115 of optically transparentsubstrate 215 if it is made of sapphire. Typical root mean square (rms)roughness after polishing is about 20-50 Angstrom. Adequate surfaceroughness on the side of optically transparent substrate 215 exposed tothe excimer laser is a critical aspect of the laser lift-off process.Destructive interference due to the formation of a Fabry-Perot cavitymay occur within an optically transparent substrate 215 that is highlypolished on the front side and backside 1115. The destructiveinterference attenuates the laser energy flux through opticallytransparent substrate 215. The Fabry-Perot cavity may be eliminated byroughening one side of the polished surface of optically transparentsubstrate 215. In an embodiment in accordance with the invention,backside 1115 of optically transparent substrate 215 is roughened bysand blasting backside 1115 to reduce its reflective properties to theorder of the polished surface roughness achieved using diamond grit.

An important aspect to the laser lift-off process is the attachment ofsupport substrate 1105. The bonding interface between the semiconductormembrane 1110 and support substrate 1105 must withstand thethermoelastic stress wave associated with the rapid heating and coolingof the semiconductor thin film during the laser processing.Additionally, support substrate 1105 must match the characteristicimpedance of semiconductor membrane 1110 in order to minimize the effectof a reflected stress wave that may degrade the transferred film. For asingle transfer process to be used bonding material 1106 and supportsubstrate 1105 are required to fulfill the following conditions: 1) thebond is electrically and thermally conductive, 2) possess the same orsimilar characteristic impedance, and 3) robust enough to withstandtypical laser device processing.

A two-step transfer process in an embodiment in accordance with theinvention provides greater flexibility to integrate the nitride-baseddevice onto final substrate 1138 (see FIG. 1f). The first step involvesremoving optically transparent substrate 215 using supporting substrate1105 and bonding material 1106 selected to fulfill conditions 2 and 3above. The second step involves removal of bonding material 1106 andrelease of supporting substrate 1105 to make semiconductor membrane 1110free-standing or alternatively secondary support layer 1117 may beattached to semiconductor membrane 1110 prior to release from supportsubstrate 1105 so that semiconductor membrane 1110 is not free-standing.Semiconductor membrane 1110 is then mounted onto final substrate 1138.In a two-step process, initial bonding material 1106 (step 1) needs tobe easily removable from support substrate 1105, allowing subsequenttransfer of the semiconductor membrane 1110 from support substrate 1105onto final substrate 1138. Adding the second step removes the constraintthat conditions 1, 2, and 3 need to be fullfilled simultaneously in oneprocessing step. An embodiment in accordance with the invention uses acyanoacrylate-based bonding material 1106 to bond semiconductor membrane1110 onto impedance-matched supporting substrate 1105, typically Si, toalleviate requirements 2) and 3). Bonding material 1106 is soluble inorganic solvents allowing semiconductor membrane 1110 to be laterdetached from the support and transferred onto substrate 1138. Bondingmaterial 1106 may also be a wax, epoxy or other organically solubleadhesive.

In an embodiment in accordance with the invention, FIG. 1a showsmounting of laser diode structure 1000 to supporting substrate 1105 withwax, epoxy or ethyl-cyanoacrylate-based bonding material 1106 to providesupport for the semiconductor membrane 1110 after removal of opticallytransparent substrate 215 and prior to transferring semiconductormembrane 1110 onto final substrate 1138. P-contact 1020 provides anelectrical contact to laser diode structure 1000. FIG. 1b shows exposureof substrate 215 and semiconductor membrane 1110 to ultraviolet excimerlaser light 1120. Proper adjustment of the excimer laser (not shown)allows decomposition of thin GaN layer 1130 at the interface betweenoptically transparent substrate 215 and semiconductor membrane 1110. GaNlayer 1130 is decomposed into Ga metal and N₂.

For a XeCI excimer laser operating at 308 nm the laser energy rangeafter passage through a homogenizer is typically about 300 to 600 mJ/cm²with a beam size of about 5 mm by 5 mm. A homogenizer converts aGaussian-like laser beam to a flat plateau-like laser beam whichprovides improved beam uniformity. Larger areas may be exposed byscanning the laser beam across backside 1115. The excimer laser istypically pulsed in the range of 1-10 Hz with one pulse typically beingsufficient to achieve decomposition of GaN layer 1130. Backside 1115allows uniform excimer laser exposure of GaN layer 1130. FIG. 1c showsseparation of sapphire substrate 215 from semiconductor membrane 1110 atthe interface by heating laser diode structure 1000 (see FIG. 1a) whichis bonded to support substrate 1105 to a temperature in the range ofabout 30°-70° C. Residual Ga metal layer 1130 on semiconductor membrane1110 at the interface is removed with a hydrochloric acid (HCl) dip thatis equal parts distilled water. Approximately 1 μm of the damaged filmat the interface on semiconductor membrane 1110 is removed bydry-etching in an Ar/Cl₂/BCl₃ gas mixture. Typically, chemicallyassisted ion beam etching (CAIBE) or reactive ion etching (RIE) is usedfor the dry-etch. Low energy (less than about 400 eV) Ar ion sputteringis employed after the dry-etch to reduce any surface damage caused bythe dry-etching.

Once semiconductor membrane 1110 is detached and transferred fromoptically transparent substrate 215 (FIG. 1c), secondary support layer1117 is then attached onto semiconductor membrane 1110 bonded to supportsubstrate 1105 (FIG. 1d). Attachment of secondary support layer 1117 mayalso follow deposition of n-metal layer 1118 or secondary support layer1117 may be directly attached onto membrane 1110. Ideally n-metal layer1118 is chosen so that it provides a low contact-resistance ohmicbackside n-contact. Secondary support layer 1117 will act as anintermediate transfer and bonding layer to final substrate 1138.Typically, secondary support layer 1117 is an elastically-compliantmaterial such as indium, gold, copper or silver which also possesseshigh electrical and thermal conductivity. Using a material having arelatively low melting point such as indium (T_(m)=156° C.), facilitatesa low-temperature post-laser liftoff bonding process. Secondary supportlayer 1117 also functions to stress semiconductor membrane 1110 tooppose the bowing and resultant cracking caused by the residual stresspresent in semiconductor membrane 1110 due to release of semiconductormembrane 1110 from optically transparent substrate 215. The stress istypically about 0.4 GPa for semiconductor membrane 1110 which istypically a 3 μm thick GaN film.

Secondary support layer 1117 may also function as the n-contact tosemiconductor membrane 1110. Typically, 3-5 μm thick indium is chosenfor secondary support layer 1117 and secondary support layer 1117effectively bonds semiconductor membrane 1110 onto final substrate 1138.After depositing secondary support layer 1117, semiconductor membrane1110 and support structure 1105 are immersed in an organic solvent torelease the ethyl-cyanoacrylate adhesive layer from step 1 describedabove (see FIG. 1e).

With reference to FIG. 1f, metal back-contact layer 1121, typically madeof Ti/Au or Ti/Al is deposited by thermal or e-beam evaporation on finalsubstrate 1138 that is typically silicon, silicon carbide or diamond. Atthe bonding interface, metal contact layer 1142 and bonding layer 1141are deposited. Bonding layer 1141 may be a low-temperature metal, suchas indium, that is thermally and electrically conductive to the contactmetal. The thickness of bonding layer 1141 can vary from about 1 μm to 5μm. With reference to final substrate 1138, silicon is an economicalsubstrate material that is electrically and thermally (about 1.5 W/cmKat room temperature and about 0.97 W/cmK at 100° C.) conductive andallows mirror cleaving and integration of a silicon driver chip withlaser diodes. Silicon carbide is an expensive substrate material that iselectrically and thermally (about 5 W/cmK at room temperature and about3.2 W/cmK at 100° C.) conductive and allows mirror cleaving. Diamond isa very expensive substrate material that is the best known thermalconductor (about 20 W/cmK at room temperature and about 15.5 W/cmK at100° C.) and can be metalized to be conductive while allowing mirrorcleaving. Structure 1300 is attached to structure 1350 as shown in FIG.1f to create final structure 1400 shown in FIG. 1g. FIG. 1h shows fourlaser array 1301 made in essentially similar fashion to single laserstructure 1300.

Alternatively, structure 1300 in FIG. 1f can be mounted directly ontothe sub-mount of a laser package after cleaving or dicing semiconductormembrane 1110 into individual dies. If a low-melting point metal, suchas In (indium), is deposited as secondary support structure 1117 then alow-temperature anneal may be used to improve the bond interface betweensemiconductor membrane 1110 and the final substrate 1138. By meltingsecondary support layer 1117 and metal bonding layer 1141, anyparticulates or asperities may be consumed when the metal interfacemelts, improving the adhesion of the film. Because the secondary supportlayer 1117 is elastically compliant, the adhesion of the device canfurther be improved by mechanically pressing semiconductor membrane 1110onto final substrate 1138.

The use of a low-melting point metal, such as indium, for bonding at thebond interface does not allow n-metal layer 1118 to be alloyed since themelting point of indium metal in secondary support layer 1117 andbonding layer 1106 is below the alloying temperature of n-metal layer1118, typically about 500° C. for Ti/Al (see FIG. 1d). One solution ishaving the final substrate 1138 coated with metal layer 1141 that isreactive to the secondary support layer 1117. For example, Pd and In fora Pd:In ratio of 1:3, react at low temperatures (T˜200° C.) to form theintermetallic PdIn₃ which has a melting point of 664° C. (see W. S. Wonget al. J. Electron. Mater. 28, 1409 (1999)). After creating finalstructure 1400 using intermetallic PdIn₃, final structure 1400 may beheated to 500° C. for alloying n-metal layer 1118. Other methods havealso been demonstrated by using Van der Waals forces to bondfree-standing membranes onto other substrates (see E. Yablonovitch, T.Gmitter, J. P. Harbison, and R. Bhat, Appl. Phys. Lett. 51, 2222 (1987),and T. Sands, U.S. Pat. No. 5,262,347).

A solder layer may also be used for bonding layer 1141. Depending on thecomposition of bonding layer 1141 and final substrate 1138, bondinglayer 1141 and final substrate 1138 are heated to the appropriatebonding temperature in a forming gas atmosphere to avoid oxideformation. A bonding temperature of about 180° C. is typically used whenusing indium for bonding layer 1141. If a Pd or Au film has not beendeposited on the exposed surface of bonding layer 1141, flux or ahydrochloric acid dip prior to heating may be used to remove any oxidepresent on the exposed surface of bonding layer 1141. Other well-knowntechniques for oxide removal may also be used. When using PbSn forbonding layer 1141, a bonding temperature of about 220° C. is typicallyused. Oxide may be removed as described above prior to bonding if an Aufilm has not been applied to the exposed surface of bonding layer 1141.

In an embodiment in accordance with the invention, Au—Authermo-compression bonding may be used to bond semiconductor membrane1110 to final substrate 1138. Au—Au thermo-compression bonding providesfor better thermal contact between semiconductor membrane 1110 and finalsubstrate 1138. Note, bonding layer 1141 is not present if Au—Authermo-compression bonding is used to join final substrate 1138 tosemiconductor membrane 1110. A typical bonding temperature for Au—Authermo-compression is about 350° C.

Final structure 1400 (FIG. 1g) is cooled to about 20° C. while a bondload is applied. For example, the bond load used with In or PbSn solderis about 200 grams if the bonding area is 25 mm². If Au—Authermo-compression bonding is used, the bond load is typically about1500 g/mm².

In addition, in an embodiment in accordance with the invention, thesecondary support can be engineered to maintain the intrinsic residualstress of semiconductor membrane 1110 thus minimizing the possibility ofmechanical failure of semiconductor membrane 1110. For example, a 1 μmthick sputtered MoCr film may be manipulated to possess an internalstress gradient between 1 GPa compressive to tensile by varying thesputtering process pressure during deposition (e.g. see U.S. Pat. No.5,914,218). These stresses are adequate to offset the residualcompressive stress in GaN-based materials typically reported to be 0.4-1GPa. The secondary support layer 1117 can effectively stress thefree-standing membrane in an opposing gradient thereby removing anybowing and assist in flattening the device structure for subsequentlayer transfer.

Another embodiment in accordance with the invention (see FIGS. 2a-2 band FIGS. 3a-3 b) attaches support layer 1119 onto support structure1105 and semiconductor membrane 1110 structure after liftoff (see FIG.1d) and prior to solvent immersion (see FIG. 1e). Support layer 1119(approximately 100-500 μm thick) acts as a new host substrate for thesemiconductor membrane 1110 after release from support structure 1105.This step eliminates the need to handle free-standing semiconductormembrane 1110. Support layer 1119, such as a Cu layer which is a goodthermal conductor (about 4 W/cmK), is typically deposited byelectroplating at room temperature onto exposed semiconductor membrane1110 creating semiconductor membrane 1110 attached to Cu support layer1119. New support layer 1119 is structurally strong enough to withstandhandling but also thin enough to allow semiconductor membrane 1110 to becleaved to form parallel mirror facets. Other metals such as Ni or Auare also possible for support layer 1119. This approach is readilyapplicable to laser diode array structures as shown in FIGS. 3a and 3 bfor four laser diode array structure 1301.

In an embodiment in accordance with the invention, cleaved facets can beachieved on free-standing semiconductor membrane 1110 by cleaving alongthe {1100} plane of semiconductor membrane 1110 or after attachingmembrane 1110 to final substrate 1138. In order to cleave alongcrystallographically oriented substrates, the vertical crystal planes ofsemiconductor membrane 1110 are aligned with the appropriate crystalplanes of silicon, silicon carbide or diamond final substrate 1138 toallow for cleaving after bonding as shown in FIG. 1g. FIG. 4 shows adesired alignment of the relevant crystal planes of semiconductormembrane 1110 and final substrate 1138 prior to cleaving. Devices arecleaved along the {1100} planes of semiconductor membrane 1110 and the{111} planes of final substrate 1138. FIG. 5 shows the relevant crystalplanes of semiconductor membrane 1110 and final substrate 1138 aftercleaving for gallium nitride and silicon, respectively. Cleaved facet1295 is also shown.

In an embodiment in accordance with the invention, FIG. 6 shows adesired alignment of the relevant crystal planes of semiconductormembrane 1110 and final substrate 1138 prior to cleaving. In FIG. 6, the{111} crystal plane of final substrate 1138 is parallel to the {1100}crystal plane of semiconductor membrane 1110. This orientation allows aneasier cleave of final substrate 1138 as seen in FIG. 7 which shows therelevant crystal planes of semiconductor membrane 1110 and finalsubstrate 1138 after cleaving.

After proper alignment of the relevant crystal planes of semiconductormembrane 1110 and final substrate 1138, semiconductor membrane 1110 isbonded to final substrate 1138 in an embodiment in accordance with theinvention. Layer 1141 is used for bonding. In the case of using areactive metal bond interface, bonding layer 1141 and final substrate1138 are heated to the appropriate bonding temperature in a forming gasatmosphere to avoid oxide formation.

Cleaving of laser diode facets 1295 (see FIGS. 5 and 7) is accomplishedby propagating the cleave from the edge of, typically, silicon, siliconcarbide or diamond final substrate 1138 into semiconductor membrane1110. Alternatively, laser diode facets 1295 may be dry-etched usingCAIBE in an Ar/Cl₂/BCl₃ gas mixture. The reflectivity of the laser diodefacets 1295 may be increased by deposition of SiO₂/TiO₂ or SiO₂/HfO₂high reflective coating using, for example, e-beam evaporation.

In an embodiment in accordance with the invention, cleaved facets mayalso be made on semiconductor membrane 1110 attached to secondarysupport layer 1117 prior to bonding to final substrate 1138.Semiconductor membrane 1110 is cleaved along {1100} plane and thenmounted onto final substrate 1138. This eliminates the need to alignsemiconductor membrane 1110 with final substrate 1138. This process alsoallows placement of cleaved semiconductor membrane 1110 onto non-singlecrystal or amorphous substrates such as glass, plastic or metal.

While the invention has been described in conjunction with specificembodiments, it is evident to those skilled in the art that manyalternatives, modifications, and variations will be apparent in light ofthe foregoing description. Accordingly, the invention is intended toembrace all other such alternatives, modifications, and variations thatfall within the spirit and scope of the appended claims.

What is claimed is:
 1. A method for making a nitride laser diodestructure comprising: providing a semiconductor membrane having anoptically transparent substrate attached on a first side of saidsemiconductor membrane; attaching a support substrate to a second sideof said semiconductor membrane; removing said optically transparentsubstrate from said first side of said semiconductor membrane; placingan elastically-compliant support layer on said first side of saidsemiconductor membrane; releasing said semiconductor membrane from saidsupport substrate; and placing said elastically-compliant support layeron a substrate having a high thermal conductivity.
 2. The method ofclaim 1 wherein said optically transparent substrate is comprised ofsapphire.
 3. The method of claim 1 wherein the step of attaching saidsupport substrate to said second side of said semiconductor membraneincludes using wax to attach said support substrate to said second side.4. The method of claim 1 wherein said semiconductor membrane iscomprised of In, Ga, Al and N.
 5. The method of claim 1 wherein saidthermally conducting substrate includes a material selected from thegroup consisting of silicon, silicon carbide, copper, gold and diamond.6. The method of claim 1 wherein said nitride laser diode structure isan array of nitride laser diodes.
 7. The method of claim 1 wherein thestep of attaching said thermally conducting substrate to said first sideof said semiconductor membrane includes putting a solder layer on saidthermally conducting substrate.
 8. The method of claim 1 wherein thestep of removing said optically transparent substrate includes exposingsaid optically transparent substrate to laser light.
 9. The method ofclaim 3 wherein said solder layer includes a material selected from thegroup consisting of In, PbSn, and AuSn.
 10. The method of claim 6wherein the step of removing said optically transparent substrateincludes polishing of said optically transparent substrate prior toexposure to laser light.